Add Basho to the companies looking to take a chunk of the cloud storage space. Today, the company announced RiakCS, a “multi-tenant, distributed, S3-compatible cloud storage platform” that runs on top of the Riak-distributed database. The question isn’t really whether Basho can cut into Amazon’s business, but how much.

According to J.P. Morgan analyst Doug Anmuth, Amazon Web Services overall is expected to be a $2.6 billion business by 2015. S3 is a pretty big chunk of that.

We’ve noted previously that Amazon S3 is seeing staggering growth. According to stats from January, Amazon had 762 billion objects stored in S3. That’s a year-over-year growth of 192%, says AWS evangelist Jeff Barr.

RiakCS Versus Amazon S3

Is RiakCS competitive with Amazon S3? I guess that depends on your criteria. The feature-set for RiakCS looks competitive. According to the “Building Your Storage Cloud,” (PDF) white paper from Basho, RiakCS looks like a robust and S3-compatible system.

The company is targeting service providers that might want to offer S3-compatible storage or Dropbox-like services, and companies that might want to host their own S3-compatible storage.

Note that the Basho white paper is inaccurate in at least one regard. The paper claims that Amazon offers “no guarantee of service – Amazon does not provide or offer a service level agreement to customers.” Actually, Amazon does provide an S3 SLA, which promises “commercially reasonable efforts to make Amazon S3 available with a Monthly Uptime Percentage (defined below) of at least 99.9% during any monthly billing cycle.” If S3 is unavailable for some reason, customers can get a 10% credit for uptime less than 99.9% but more than 99%. They can receive a 25% credit for less than 99%.

It may not be a very good SLA, but it’s an SLA.

There’s at least one feature discrepancy between S3 and RiakCS, in terms of supported object size. RiakCS has a 5GB limit on object size, whereas Amazon S3 has a 5TB limit. Note that Amazon’s object-size limit was 5GB until December of 2010, and was raised in part to cope with use cases like storing uncompressed movie files.

Pricing should be to Basho’s advantage, kind of, for large-scale storage problems. When I asked Basho about its pricing, I was told that prices start at $10,000 per storage server. Assuming a 24TB server, they say, you should be looking at about $0.40 per GB total for the cost of RiakCS alone.

Amazon, on the other hand, starts at $0.093/GB per month for reduced redundancy storage or $0.125/GB per month for regular S3. Amazon’s simple monthly calculator says that 24TB of storage will run about $2,718 a month, which means you’d pay off the licensing fees in less than four months.

On the other hand, the $0.40/GB cost that is projected by Basho doesn’t take into account any hardware, energy or personnel costs.

RiakCS isn’t the only game in town, of course. Eucalyptus Walrus provides an S3-compatible storage layer that companies could build on without any costs, though it doesn’t seem to be quite as full-featured as RiakCS – particularly when it comes to the reporting/accounting features for RiakCS.

If you’re looking at alternatives to Amazon S3, what features are most important? Is it enough for a company to offer a solid on-premises solution, or is there something that would make a cloud-storage offering the category killer?